Using a new and more detailed approach to diffusion tensor imaging (DTI) recently developed in their laboratories, the investigators aim to confirm and expand upon previous findings of white matter abnormalities throughout the brain in individuals with autism. They have chosen to focus particularly on cerebellar and motor pathways in consideration of the prevalence of motor deficits in autism as well as brain structural studies that have indicated cerebellar abnormalities in autistic children. In addition, they propose to investigate a possible functional association between white matter structure and the expression of restricted repetitive behaviors in autistic children, by correlating measures of white matter integrity with behavioral assessments indicating the severity of various forms of restricted repetitive behaviors. Two aims will be accomplished. Specific Aim 1 will examine the integrity of white matter pathways in high functioning autistic children. It is hypothesized that autism is associated with specific white matter abnormalities in the cerebellum and other motor circuits. Additionally, the investigators expect to confirm and expand on previous reports of cerebral abnormalities by using newly developed DTI methods. Specific Aim 2 will determine whether there is a relationship between white matter abnormalities and the occurrence of restricted repetitive behaviors in children with autism. It is hypothesized that differences in the occurrence and type of restricted repetitive behaviors among autistic individuals are correlated with specific regional white matter abnormalities. Results from the proposed experiments should contribute to current knowledge of brain abnormalities in autism and their relationship to restricted repetitive behaviors, and may be relevant to understanding the mechanisms underlying motor deficits in this disorder. [unreadable] [unreadable] [unreadable]